The present invention relates to radio communications apparatus, and more particularly, to radio antenna apparatus.
Computing devices, such as laptop computers, notebook computers, pocket PCs, personal digital assistants (PDAs), gaming devices, and the like, now commonly possess wireless communications capabilities. For example, many laptop and notebook computers now incorporate radio communications circuitry configured to communicate with, for example, WiFi networks and/or public cellular networks. Such circuitry may be integrated in the computer and/or may be provided in a circuit assembly, such as a PC card or a USB adapter, which is plugged into the computer. Similar cards and/or adapters may be used with other electronic devices, such as PDAs and computer peripherals (e.g., printers, scanners, and the like).
Such wireless communications circuitry may be configured to connect to an external radio antenna and/or may include an integrated radio antenna. Some PC cards, for example, include an external antenna jack to which a rigid antenna and/or an antenna cable may be attached. A number of PC cards are also available which include an internal antenna without an external antenna connection. For example, a GC-89 GPRS/WiFi PCMCIA card marketed by Sony Ericsson Mobile Communications, Inc., includes an internal antenna that is positioned within a housing proximate an end of the card. Many WiFi cards have a similar internal antenna configuration.
Constraints on the size and positioning of such internal antennas may cause antenna performance to be significantly degraded. For example, when a wireless PC card is mounted in a notebook computer, the antenna of the card may be blocked or shadowed by the LCD screen of the computer. This blockage or shadowing can result in a reduction of gain in certain directions. In addition, when the computer is in a normal operating position, the polarization of the antenna may be dominant in a horizontal plane. However, in certain fringe areas of low signal coverage, signal polarization may be dominantly vertical. The resulting polarization mismatch may lead to significant performance degradation.